They are two men who, according to prosecutors, never wielded a gun during a bloody 2012 firefight outside a Puerto Rican social club in Bethlehem.

Yet, Luis Rivera and Jose Gonzalez both had gunshot residue on their hands after the fatal shootout — while one of two defendants charged in the melee did not.

Those test results — seized upon by the defense and downplayed by the prosecution — were outlined Tuesday by a forensic scientist during the ninth day of testimony in Rene Figueroa and Javier Rivera-Alvarado's trial in Northampton County Court.

After the shooting that killed a 23-year-old woman and wounded five other people, investigators had samples from seven individuals analyzed for gunshot residue. Only three — Figueroa on the defense side, and cousins Rivera and Gonzalez, who were witnesses for the prosecution — tested positive, their hands containing particles of three chemicals linked to gunfire.

So testified Stephanie Horner, who specializes in residue analysis. But walked through the results by First Deputy District Attorney Terence Houck, Horner said she could not say whether any of the three men actually fired a gun. Just as probable, she said, was that they were in the vicinity of someone who did so, or touched something on which gunshot residue had came to rest.

Houck argues that Rivera, who was shot in the knee early that morning, could have gotten residue on his hands from his own wound. Gonzalez, Houck says, may have gotten his while tending to his injured relatives after the firefight.

"Those particles can be transferred from one person to the other," Horner agreed.

But whether that possibility represents what really happened is a key battleground in the trial, with lawyers for Figueroa and Rivera-Alvarado insisting that Houck's explanation is a stretch. More plausible, the defense suggested, was that each of the men with residue on his hands used a firearm during the melee.

"Your findings are consistent with Jose Gonzalez firing a gun, Luis Rivera firing a gun and Rene Figueroa firing a gun?" asked Figueroa's attorney, Jack McMahon, who argues his client pulled a weapon only in self-defense.

"Correct," acknowledged Horner, though she said the findings were consistent with other scenarios as well.

Jurors must decide whether Rivera-Alvarado and Figueroa were the aggressors in the Dec. 2, 2012, gun battle that authorities have labeled one of the Lehigh Valley's worst. The stakes are high, with Figueroa facing the death penalty if convicted of murdering Yolanda Morales of Bethlehem, who was gunned down during the firefight.

Rivera-Alvarado, 34, and Figueroa, 40, both Allentown are accused of crimes that include attempted murder, conspiracy and aggravated assault, though only Figueroa is charged with homicide.

The shooting occurred after a minor incident in the Puerto Rican Beneficial Society spilled onto East Third Street, according to testimony. Three others were injured, as were the defendants, both of whom also suffered gunshot wounds.

Their attorneys maintain they were the victims and not the perpetrators. It was the prosecution's star witness, Orialis Figueroa of Easton, who started the violence and whose reckless gunfire killed Morales, the defense maintains. (Orialis Figueroa is of no relation to Rene Figueroa).

That Rivera-Alvarado did not test positive for gunshot residue was not unexpected, considering testimony that his blood-covered hands were washed at St. Luke's University Hospital, where he was taken for his injuries. Defense lawyer Edward Andres says his client never had a gun, and he noted Tuesday that the results cannot show that he ever did.

Orialis Figueroa has testified that he took a handgun off of Rivera-Alvarado after knocking him out with a baseball bat in self-defense. But though Orialis Figueroa admitted he also fired that gun, he did not test positive for gunshot residue either.

A lot of factors can cause gunshot residue to be lost, Horner said: movement, the passage of time, the washing or wiping of hands, the presence of blood or sweat, or even a rainy or windy day.

Also Tuesday, a juror with a work commitment was excused from the panel because of how long the trial has stretched. She was replaced by an alternate, a man, with the jury now equally split between men and women.

Judge Anthony Beltrami said he expects testimony will conclude early next week.